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A/C Air Conditioner Diagnostics with trouble codes list, Reset, Sensor Data

How to troubleshoot Mercedes Benz Air Conditioner System, Read Sensor Data, Reset Unit

If you have this A/C unit follow these steps to troubleshoot your Mercedes Benz Air Conditioner System
If you have this A/C unit follow these steps to troubleshoot your Mercedes Benz Air Conditioner System

Troubleshooting Instructions
Entering Diagnostic Trouble Code (DTC) Display Mode

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1) Turn ignition on. Press down arrow push button until “LO” is shown in A/C-heater control panel temperature display window.
2) Within 20 seconds, simultaneously press REST and defrost push buttons for more than 2 seconds. The Light Emitting Diode (LED) in the recirculated air push button will blink and the display window will show “di R”.3) Press AUTO push button repeatedly, recording each DTC,until all DTCs are displayed. Permanent malfunctions are displayed first. See DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION tables.
4) If no permanent malfunctions are stored, the display window shows “En d”. Press AUTO push button again. Intermittent DTCs will be displayed. Intermittent malfunctions are recognizable by the degree (°) symbol displayed along with the DTC (example: “04 °”).
5) If no intermittent malfunctions are stored, the display window shows “En° d”. Proceed to ERASING DIAGNOSTIC TROUBLE CODES.

Erasing Diagnostic Trouble Codes
1) After display window shows “En° d”, press AUTO push button once again. Display window should show “dE L” (delete).
2) To erase DTCs, simultaneously press down and up arrow push buttons for more than 5 seconds. The display window should show “- –“. If not erasing DTCs, press the AUTO push button. The permanent DTCs will again be displayed. Proceed to EXITING DTC DISPLAY MODE.
Exiting DTC Display Mode
Simultaneously press down and up arrow push buttons until the pre-selected temperature setting of “72 °F” is displayed. Turn ignition off.

DCT error codes list:

B1226 – In-car temperature sensor (B10/4)
B1227 – Outside temperature indicator temperature sensor (B14)
B1228 – Heater core temperature (B10/1)
B1229 – Heater core temperature (B10/1)
B1230 – Evaporator temperature sensor (B10/6)
B1231 – ECT sensor (B11/4)
B1232 – Refrigerant pressure sensor (B12)
B1233 – Refrigerant temperature sensor (B12/1)
B1234 – Sun sensor (B32)
B1235 – Emissions sensor (B31)
B1241 – Refrigerant fill
B1416 – Coolant circulation pump (M13)
B1417 – Duovalve (Y21y1), left
B1418 – Duovalve (Y21y2), right
B1419 – Electromagnetic clutch (A9k1)
B1420 – Idle speed increase
B1421 – Pulse module (N65)
B1422 – Series interface (K1) connection to instrument cluster (A1)
B1423 – Switchover valve block (Y11)
B1424 – Activated charcoal filter actuator (A32m2) open
B1425 – Activated charcoal filter actuator (A32m2) closed
B1432 – Non-USA DTC
B1459 – Series interface (K2) connection to instrument cluster (A1)
B1462 – Wide open throttle (WOT) position signal: diesel engines

 

Climate control as a diagnostic tool

READING SENSOR VALUES

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1) Turn ignition on. Simultaneously press down and up arrow push buttons until the pre-selected temperature setting of “72 °F” is displayed. Press the AUTO push button.
2) Press REST push button for more than 6 seconds. The display window will alternately show “01” and an in-car temperature of “72 °F”, or “LO” if there is an open circuit, or “HI” if there is a short circuit.
3) By pressing the windshield air distribution push button, the next ascending test step is displayed. By pressing the footwell air distribution push button, the next descending test step is displayed. See SENSOR VALUE DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table. Press REST push button to exit reading sensor values mode.

01 = In-car temp sensor

02 = outside temp sensor

03 = left heat exchanger (heater core) temp sensor

04 = right heat exchanger sensor

05 = evaporator sensor

06 = coolant temp

07 = refrig. pressure in bar

08 = refrig temp sensor (23*9 = 23.9deg C)

09 = nothing

10 = Blower control voltage (great for evaluating blower controller problems)

11 = emissions sensor (B31) e.g. 3.1 = 31.v

12 = sun sensor 4.2 = 4.2v

20 = aux fan control 6.1 = 6.1ma (max 10ma)

21 = engine speed

22 = vehicle speed

23 = Circuit 58d e.g. 99 = 99% of battery voltage

24 = BATTERY VOLTAGE e.g. 12.5 = 12.5v

30 = left rear air conditioning heat exchanger temp sensor (not all vehicles; obviously)

31 = right side

32 = rear evap temp sensor

33 = blower control voltage rear 0.8(MIN) – 6.0(MAX)

34 = left rear temp selector

35 = right side

38 = software status e.g. 37 rear air conditioning

38 = hardware status e.g. 37 , rear air conditioning

40 = control module version software status (?)

41 = control module version menu hardware status

42 = control module variant code 1st number

43 = variant code second number.

4 comments

  1. Just got price for ac condenser $3200 for a 2003 SL500 (42,000mi) Mercedes 42,000 mi

  2. need earlier version 2002 without digital readout

  3. Having 3 different MB models – all of them start displaying sensors after pressing REST, but here is where the different scrolling applies. (when you have climatronic with no REST button, you need to use advanced scanner, or replace climatronic with one having REST)
    -on single zone R129 you scroll by pressing fan buttons
    -on dual W210 you scroll by pressing left and right Auto
    -on 4-zone W211 you scroll by pressing left temp adjustment.
    4 zone displays more sensors
    00 has to be inside cabin per my observation, so my guess 00 and 01 are front and rear of the cabin, but could never find official data.

  4. Good info, but does not explain how to use the data.
    Per my experience you need to read the sensors at least twice in different conditions.
    1 on cold car before engine start and before sun can warm the cabin. All the temperature sensors should show the same, usually with +- 3F differences. Very common evaporator sensor failure will show temperature very high
    2 a minute after restarting car that was sitting on hot parking lot. This will allow to see if compressor is building the pressure and how the cores work.

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